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Microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

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Transactions of Nonferrous Metals Society of China 2016年第8期26卷 2029-2042页

作者： M.S.SALLeH M.Z.OMAR K.S.ALHAWARI M.N.MOHAMMeD M.A.MAD ALI e.mohamad Department of Manufacturing Process Faculty of Manufacturing Engineering Universiti Teknikal Malaysia Melaka Department of Mechanical and Materials engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of engineering and Technology Faculty of Information Sciences and EngineeringManagement and Science University

The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SeM), energy dispersive X-ray (eDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

关键词： aluminium alloy thixoforming T6 heat treatment mechanical properties

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Feasibility of Solar Tracking System for PV Panel in Sunbelt Region

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Journal of Modern Power Systems and Clean energy 2021年第2期9卷 395-403页

作者： Soulayman Soulayman mohamad Hamoud mohamad-Amir Hababa Wassim Sabbagh the Department of Applied Physics Higher Institute for Applied Sciences and TechnologyDamascusP O Box 31983Syria

In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owing to the overheating that results from excessive exposure to solar *** conclusion has been formulated based on a mathematical model,which in turn is based on the assumption that the PV module temperature can be calculated using an empirical relation of this temperature to ambient temperature,available solar irradiance,and nominal operation cell temperature(NOCT).To support this conclusion,it is claimed that the mathematical model is validated ***,this assumption is vague and widely used in the *** objective of the present work is to reevaluate the above-mentioned assumption and to discuss the results deriving from *** is shown experimentally in the present work that the above-mentioned assumption overestimates the PV module *** a solar irradiance of 900 W/m2,ambient temperature of 25℃,and wind speed of 5 m/s,the measured PV module temperature is lower than the value calculated based on the mentioned assumption by 29.26%.

关键词： Photovoltaic(PV)module temperature wind speed influence PV module efficiency experimental verification Damascus clear-sky conditions

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exploring the influence of optical and thermal parameters on the effectiveness of parabolic trough collector receiver units

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Clean energy 2024年第4期8卷 15-33页

作者： Khaled mohamad engineering and Natural Sciences Faculty SDU UniversityAlmatyKazakhstan

This study investigates the optimization of physical parameters in a parabolic trough collector receiver unit to improve its thermal and optical *** parameters include the transmissivity,reflectivity,absorptivity,emissivity and thermal conductivity of the outer cover and absorber *** study utilizes a novel experimental design and a simulation model that accounts for the infrared reflectivity inside the *** simulation results were validated by the experimental data,with a maximum deviation of 8%.The study analyses the effects of varying the physical parameters on the heat transfer fluid temperature,total plant efficiency,temperature profiles,temperature gradients and thermal *** study finds that increasing the reflectivity and decreasing the emissivity of the outer cover and the absorber pipe significantly enhance the performance,with maximum increases of 25.8%and 26.5%in total efficiency,*** study also finds that increasing the thermal conductivity of the absorber pipe reduces the temperature gradients and thermal stress,with maximum decreases of 42.2%and 29%,*** study provides valuable insights for optimizing the receiver design and operation in solar-thermal systems.

关键词： parabolic trough collector heat transfer fluid receiver unit outer cover absorber pipe

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Self-excitation of neurons leads to multiperiodicity of discrete-time neural networks with distributed delays

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Science China(Information Sciences) 2011年第2期54卷 305-317页

作者： SANNAY mohamad Department of Mathematics Faculty of Science Universiti Brunei Darussalam

In this paper, we investigate the interesting multiperiodicity of discrete-time neural networks with excitatory self-connections and distributed delays. Due to self-excitation of neurons, we construct 2N close regions in state space for N-dimensional networks and attain the coexistence of 2N periodic sequence solutions in these close regions. Meanwhile we estimate exponential attracting domain for each periodic sequence solution and apply our results to discrete-time analogues of periodic or autonomous neural networks. Under self-excitation of neurons, numerical simulations are performed to illustrate the effectiveness of our results.

关键词： self-excitation multiperiodicity discrete-time neural networks distributed delays

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Adaptive energy consumption scheduling of multi-microgrid using whale optimization algorithm

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International Journal of Modeling, Simulation, and Scientific Computing 2021年第5期12卷 78-96页

作者： mohamad Abedini mohamad Mostafai Department of electrical engineering Faculty of Engineering Ayatollah Boroujerdi UniversityBoroujerdIran Faculty of engineering Lorestan Branch Islamic Azad University of DoroodDoroodIran

In this paper, we investigated the day-ahead scheduling of network consisting of severaldistributed generation sources and connected loads. This scheduling is an optimization problem that has two objective functions, namely, operating costs and the costcaused by the emission of pollutants. In this scheduling, while introducing a new structure for micro-grid utilization, the possibility of exchanging power among networks andexchanging power between networks and the upstream distribution network is *** uncertainty of distributed wind generation sources and solar units has been investigated using appropriate probabilistic distributions. Incent-driven load-responsivenessmanagement programs have been used as to encourage subscribers to reduce their powerconsumption during high-load hours. Whale optimization algorithm has been used forscheduling of network.

关键词： Wind turbine battery optimization uncertainty

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Design of a high-frequency transformer based on amorphous cut cores for insulation breakdown testing

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High Voltage 2024年第5期9卷 1183-1194页

作者： Gijs Lagerweij mohamad Ghaffarian Niasar Prodrive Technologies SonThe Netherlands High Voltage Technologies Electrical Sustainable EnergyDelft University of TechnologyDelftThe Netherlands

Innovative test methods are required to keep up with the increased demand for insulation materials which can withstand the high-frequency square-wave voltages generated by power-electronic *** systems using high-voltage,high-frequency transformers have proven versatile and easy to *** authors investigate the application of amorphous cut cores in such *** and numerical models for the transformer and its frequency response are developed,aiding the design *** amorphous core-based transformer is designed for 8 kVpk output at 100 kHz and compared to two previous designs based on ferrite *** frequency and pulse response,as well as the high-voltage and thermal performance,are *** comparison shows that while the low parasitics of the amorphous-based transformer allow for superior frequency response,they are unsuitable for long-duration tests with high pulse repetition frequencies(25-100 kHz)due to increased core *** partial discharge inception and flashover voltage are comparable to the ferrite-based transformers.

关键词： ferrite amorphous high

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early therapeutic effect of platelet-rich fibrin combined with allogeneic bone marrow-derived stem cells on rats’ critical-sized mandibular defects

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World Journal of Stem Cells 2020年第1期12卷 55-69页

作者： Muhammad A Awadeen Fouad A Al-Belasy Laila e Ameen mohamad e Helal Mohammed e Grawish Department of Oral Biology Faculty of Oral and Dental MedicineDelta University for Science and TechnologyMansoura 11152Egypt Department of Oral Surgery and Anesthesia Faculty of Oral and Dental MedicineDelta University for Science and TechnologyMansoura 11152Egypt Department of Oral Biology Faculty of DentistryMansoura UniversityMansoura 35516Egypt

BACKGROUND Critically sized bone defects represent a significant challenge to orthopaedic surgeons *** defects generally result from severe trauma or resection of a whole large *** bone grafts are the current gold standard for the reconstruction of such ***,due to increased patient morbidity and the need for a second operative site,other lines of treatment should be *** find alternative unconventional therapies to manage such defects,bone tissue engineering using a combination of suitable bioactive factors,cells,and biocompatible scaffolds offers a promising new approach for bone *** To evaluate the healing capacity of platelet-rich fibrin(PRF)membranes seeded with allogeneic mesenchymal bone marrow-derived stem cells(BMSCs)on critically sized mandibular defects in a rat *** Sixty-three Sprague Dawley rats were subjected to bilateral bone defects of critical size in the mandibles created by a 5-mm diameter trephine *** were allocated to three equal groups of 21 rats *** I bone defects were irrigated with normal saline and designed as negative *** of group II were grafted with PRF membranes and served as positive controls,while defects of group III were grafted with PRF membranes seeded with allogeneic *** rats from each group were killed at 1,2 and 4 *** mandibles were dissected and prepared for routine haematoxylin and eosin(He)staining,Masson's trichrome staining and CD68 immunohistochemical *** Four weeks postoperatively,the percentage area of newly formed bone was significantly higher in group III(0.88±0.02)than in groups I(0.02±0.00)and II(0.60±0.02).The amount of granulation tissue formation was lower in group III(0.12±0.02)than in groups I(0.20±0.02)and II(0.40±0.02).The number of inflammatory cells was lower in group III(0.29±0.03)than in groups I(4.82±0.08)and II(3.09±0.07).CONCLUSION Bone regenerative quality of critically sized mandibula

关键词： Platelet-rich fibrin membrane Bone marrow-derived stem cells Critical-sized mandibular defects Rats Histological and immunohistochemical staining

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PRePARATION, CHARACTeRIZATION AND ADHeSIVe PROPeRTIeS OF DI-AND TRI-HYDROXY BeNZOYL CHITOSAN NANOPARTICLeS

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Chinese Journal of Polymer Science 2013年第4期31卷 649-659页

作者： mohamad Taghi Taghizadeh Ali Bahadori Department of Physical Chemistry Faculty of ChemistryUniversity of TabrizTabrizIran

Modified chitosans with 3,4-di-hydroxy benzoyl groups （CS-DHBA） and 3,4,5-tri-hydroxy benzoyl groups （CS- THBA） were synthesized and their nanoparticles were prepared via ionic crosslinking by tripolyphosphate （TPP）. The chemical structure and degree of substitution （DS） of di- and tri-hydroxy benzoyl chitosans are determined by FTIR and IH- NMR spectroscopy. The morphology of particles, size distribution and zeta potential of nanoparticles were studied using transmission electron microscopy （TeM） and dynamic light scattering （DLS）, respectively. The mean diameters of particles of CS-DHBA and CS-THBA nanoparticles were 144 nm and 112 nm, respectively. It was found that the particles size decreased slightly with decreasing the degree of substitution and increasing degree of deacetylation （DD）, due to increasing of ionic crosslinking of ammonium ions and polyanions of tripolyphosphate. The TeM photographs of CS-DHBA show that these particles are spherical in shape, but the particles of CS-THBA show some aggregation. In addition, the solubility and the mechanical properties of the prepared modified chitosans and their nanoparticles were evaluated for bio-adhesive and biomedical application. The results of solubility tests indicated that, the CS-DHBA and CS-THBA have higher solubility at pH 〉 7 comparing to CS. Also the CS-DHBA, CS-THBA and their nanoparticles showed a significant adhesive capacity and enhanced tensile strength and tensile modulus.

关键词： Nanoparticles Di- and tri-hydroxy benzoyl chitosans Ionic cross linking Solubility Adhesive properties.

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Application of nano silica to improve self-healing of asphalt mixes

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Journal of Central South University 2017年第5期24卷 1019-1026页

作者： Ganjei mohamad Amin Aflaki esmail Department of Civil and environmental engineering Amirkabir University of TechnologyTehranIran

Nano silica due to its spherical shape, tiny size and higher density compared to bitumen, may have an inherent potential to improve hot mix asphalt(HMA) self-healing. In this research scanning electron microscopy(SeM) images were used to investigate size, morphology and dispersion of nano silica particles. Additionally, HMA self-healing mechanism was also examined by SeM. Furthermore, dynamic indirect tensile test(IDT) was used to evaluate HMA self-healing index. The SeM results indicated that bitumen mortar flowing into micro cracks may be one of the most important mechanisms of HMA self-healing. The experiment results also showed that modification of bitumen by nano silica promotes the ability of the HMA self-healing.

关键词： nano silica healing index Taguchi method hot mix asphalt

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COVID-19:cardiovascular manifestations-a review of the cardiac effects

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Journal of Geriatric Cardiology 2022年第3期19卷 245-250页

作者： Taha Hatab mohamad Bahij Moumneh Abdul Rahman Akkawi mohamad Ghazal Samir e.Alam Marwan M.Refaat Department of Internal Medicine Division of CardiologyAmerican University of Beirut Medical CenterBeirutLebanon

The coronavirus first reported in China in November 2002 in the form of atypical pneumonia known as the severe acute respiratory syndrome (SARS).[1] The virus then appeared in 2012 in Saudi Arabia as the Middle east respiratory syndrome (MeRS).[2] The year 2020 witnessed a novel β-coronavirus related to the previous detected viruses.[3] It was the severe acute respiratory syndrome coronavirus 2 (SARS-Co V-2)-a positive single stranded RNA virus.

关键词： acute cardiac respiratory

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